I’m loath to give advice, but . . .

For at least the first 5 years of your life as a fiction writer, stick to the short story.  Write a lot of them.  Try everything you can think of, but treat each as an opportunity to write the best short story ever written.  If you're looking for pointed craft exercises, this is where they are.  This is craft in context, where every choice you make ripples outward toward everything else.

Write a lot.  There's value in sheer quantity.

Don't hurry.  

Don't settle

Don't posture.

Empathize.  By which I mean cultivate at every turn love for the people you're writing about, and for your readers, and for yourself.  This will allow you to engage your critical sensibilities, make necessary judgements, acknowledge imperfections, and address flaws.  It will give you room for everything--tragedy, comedy, irony, satire: dramas and depictions of every hue and flavor.